Aircraft in-flight center of gravity measuring system

Abstract

In order to determine the location of the center of gravity of an aircraft in flight, an accelerometer is placed in the forward part of the aircraft and another is placed in the after part to produce signals representing the rotation of aircraft about an axis, preferably the yaw axis, through the aircraft center of gravity. The signals from the accelerometers are combined to produce a first signal having components that represent both motion of the aircraft and the location of the center of gravity along with a signal having a component representing the motion of the aircraft but substantially without a component representing the location of the center of gravity and these two signals are then combined to get a signal that represents the location of the aircraft center of gravity.

I claim: 
     
       1. An aircraft in flight center of gravity measuring system comprising: a pair of inertial sensors secured to the aircraft, each inertial sensor having a sensitive axis which is aligned so as to produce a signal representing the rotation of the aircraft about a predetermined axis through the aircraft center of gravity; and signal processing means connected to said inertial sensors including means for developing a signal from the output of the inertial sensors having components representing aircraft rotation about the predetermined axis and the location of the center of gravity and means coupled to the developing means for canceling the component representing aircraft rotation to generate a signal representing the location of the center of gravity of the aircraft while the aircraft is in flight.   
     
     
       2. The system of claim 1 wherein said inertial sensors include at least two accelerometers that generate signals representing rotation of the aircraft about said predetermined axis. 
     
     
       3. An aircraft in flight center of gravity measuring system comprising: a plurality of inertial sensors secured to the aircraft which generate signals representing rotation of the aircraft about a predetermined axis through the aircraft center of gravity, wherein the inertial sensors include at least two accelerometers that generate signals representing rotation of the aircraft about the predetermined axis; and   signal processing means connected to the inertial sensors for generating from the inertial sensors a signal representing the location of the center of gravity of the aircraft while the aircraft is in flight comprising means for generating a first signal including a component representing the location of the center of gravity and a component representing aircraft rotation about the predetermined axis, means for generating a second signal substantially without a component representing the rotation of the aircraft and means for combining the first and second signals to generate the signal representing the location of the center of gravity of the aircraft.   
     
     
       4. An aircraft in flight center of gravity measuring system comprising: a plurality of inertial sensors secured to the aircraft wherein the inertial sensors generate signals representing rotation of the aircraft about a predetermined axis through the aircraft center of gravity wherein the predetermined axis is the yaw axis of the aircraft; and   signal processing means connected to the inertial sensors for generating from the inertial sensors a signal representing the location of the center of gravity of the aircraft while the aircraft is in flight.   
     
     
       5. An aircraft in-flight center of gravity measuring system comprising: first acceleration measuring means secured to said aircraft forward of the aircraft center of gravity for generating a first acceleration signal representing rotation of the aircraft about a predetermined axis through the aircraft center of gravity;   second acceleration measuring means secured to said aircraft aft of the aircraft center of gravity for generating a second acceleration signal representing rotation of the aircraft about said predetermined axis;   first combining means connected to said first and said second acceleration measuring means for combining said first acceleration signal with said second acceleration signal to generate a first combined signal having a component representing the location of the aircraft center of gravity and a component representing rotation of the aircraft;   second combining means connected to said first and said second acceleration means for combining said first acceleration signal with said second acceleration signal to generate a second combined signal having a component representing rotation of the aircraft but substantially without a component representing the location of the aircraft center of gravity;   third combining means connected to said first and said second combining means for combining said first and said second combined signals to generate a third combined signal having component representing the location of the center of gravity but substantially without components representing rotation of the aircraft; and   center of gravity signal means connected to said third combining means for generating from said third combined signal a center of gravity signal representing the location of the aircraft center of gravity.   
     
     
       6. The system of claim 5 wherein said first combining means includes summing means to sum said first acceleration signal with said second acceleration signal to generate a summed signal. 
     
     
       7. The system of claim 7 wherein said second combing means included subtracting means for subtracting one of said acceleration signals from the other of said acceleration signals to generate a difference signal. 
     
     
       8. The system of claim 8 wherein said first combining means is connected to said second combining means and includes means for multiplying said summed signal with said difference signal to generate said first combined signal. 
     
     
       9. The system of claim 8 wherein said second combining means includes means for squaring said difference signal to generate said second combined signal. PG,15 
     
     
       10. The system of claim 6 wherein said third combining means includes means for dividing said first combined signal by said second combined signal. 
     
     
       11. The system of claim 6 wherein said first combining means includes a band-pass filter having a band-pass frequency substantially equal to the natural frequency of rotation of the aircraft about said predetermined axis. 
     
     
       12. The system of claim 5 wherein said second combining means includes a band-pass filter having a band-pass frequency substantially equal to the natural frequency of rotation of the aircraft about said predetermined axis. 
     
     
       13. The system of claim 5 wherein said center of gravity signal means includes scaling means for scaling said center of gravity signal. 
     
     
       14. The system of claim 13 wherein said scaling means includes means for adding a bias signal to said third combined signal. 
     
     
       15. The system of claim 14 wherein said scaling means includes means for multiplying the combination of said bias signal and said third combined signal by a predetermined gain factor. 
     
     
       16. The system of claim 15 wherein the values of said bias signal and said predetermined gain factor are selected as a function of the relative locations of said first and said second acceleration measuring means from a predetermined datum in the aircraft. 
     
     
       17. The system of claim 5 wherein said center of gravity means includes rate limiter means for limiting the rate of increase and decrease of said third combined signal. 
     
     
       18. The system of claim 17 wherein said center of gravity means includes a low-pass filter operatively connected to said rate limiter means. 
     
     
       19. The system of claims 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 wherein said predetermined axis is the yaw axis of the aircraft. 
     
     
       20. An aircraft in-flight center of gravity measuring system comprising: a first accelerometer secured to the aircraft forward of the aircraft center of gravity with the sensitive axis of said first accelerometer aligned such that said first accelerometer will generate a first acceleration signal that represents rotation of the aircraft about a predetermined axis of the aircraft;   a second accelerometer secured to the aircraft aft of the aircraft center of gravity with the sensitive axis of said second accelerometer aligned such that said second accelerometer generates a second acceleration signal representing the rotation of the aircraft about said predetermined axis of the aircraft;   summing means connected to said first and said second accelerometers for adding said first accelerometer signal to said second acceleration signal to produce a summed signal;   subtracting means connected to said first and second accelerometers for subtracting one of said accelerometer signals from the other to generate a difference signal;   multiplication means connected to said summing means and said subtracting means for multiplying said summed signal with said difference signal to generate a first combined signal;   squaring means connected to said subtracting means for squaring said difference signal to generate a second combined signal;   dividing means connected to said multiplication means and said squaring means for dividing said first combined signal by said second combined signal to generate a third combination signal; and   center of gravity signal means connected to said dividing means for generating from said third combination signal a center of gravity signal representing the location of the aircraft center of gravity.   
     
     
       21. The system of claim 20 additionally including a first band-pass filter connected between said first accelerometer and said summing means and a second band-pass filter operatively connected between said second accelerometer and said subtracting means. 
     
     
       22. The system of claim 21 wherein the band-pass frequency of said first and said second band-pass filter is substantially equal to the natural frequency of rotation of the aircraft about the aircraft center of gravity. 
     
     
       23. The system of claim 20 additionally including a first low-pass filter connected between said multiplication means and said dividing means and a second low-pass filter operatively connected between said squaring means and said dividing means. 
     
     
       24. The system of claim 20 additionally including a low-pass filter connected between said dividing means and said center of gravity means. 
     
     
       25. The system of claim 20 additionally including a source of bias signal connected to said center of gravity means. 
     
     
       26. The system of claim 20 wherein said center of gravity signal means includes means for scaling said center of gravity signal in relation to the relative location of said first and said second accelerometer within the aircraft. 
     
     
       27. The system of claim 20 additionally including a rate limiter connected between said divider means and said center of gravity means. 
     
     
       28. The system of claim 20, 21, 23, 24, 25, 22, 27, or 26 wherein said predetermined axis is the yaw axis of the aircraft.